http://hdl.handle.net/2122/267 Mon, 20 May 2013 01:20:17 GMT 2013-05-20T01:20:17Z http://hdl.handle.net/2122/8696 Title: The 4D imaging of the source of ground deformation at Campi Flegrei caldera (southern Italy) Authors: D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Lanari, R.; Istituto per il Rilevamento Elettromagnetico dell’Ambiente, Consiglio Abstract: We have applied a tomographic imaging technique to the inversion of a DInSAR data set at Campi Flegrei caldera. This technique allowed us to determine the temporal and spatial distribution of volumetric strain sources up to 5 km depth. Results have shown complex spatial and temporal patterns, identifying important features that were not noticed before. The first result is the observation of positive strain sources (expansion) migrating upward (in 2000 and 2006). We have interpreted them as hot fluid batches injected at the bottom of the geothermal reservoir, migrating upward and reaching the surface. Furthermore we have identified an injection episode (in 1997), which was not recognized before. This batch did not reach the surface and probably dissipated by diffusion and lateral advection without producing significant ground uplift. The injection of fluid batches does not occur at the center of the caldera, but along its borders. The three identified injection episodes (in 1997, 2000 and 2006) occur in different points. In 2000 and 2006, the injected fluids migrated, subsequently, toward the center of the caldera. Our findings agrees with results of other geophysical and geochemical studies. These results suggest a new framework for the modeling of Campi Flegrei geothermal system and for the interpretation of data recorded by the multiparametric monitoring networks on the caldera. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8696 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8692 Title: Waveform Variation of the Explosion-Quakes as a function of the eruptive activity at Stromboli Volcano Authors: Esposito, A. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Editors: Apolloni, B.; Bassis, S.; Esposito, A.; Morabito, F.C. Abstract: In the period from June to September 2011, the Stromboli volcano was affected by an activity characterized by an increase of the volcanic tremor amplitude, in the magnitude of explosions and with some lava overflows. In order to examine and understand in more detail this particular phase of the volcano, we present here an unsupervised investigation of the waveform variation of the explosion-quakes recorded during this period. The aim is to identify a possible relationship between the temporal changes of these events and the volcano seismic activity. The analysis is performed on a dataset of about 8400 explosion-quakes by using a SOM neural network. This technique works well with large datasets allowing to find out unpredicted characteristics among them. The SOM clustering highlights sudden changes occurring at the end of July and of August and a permanent variation between June and September reflecting a modification in the volcano activity. These results could be interesting for focusing the analysis of the seismological dataset in these intervals in order to evidence minor, but important variations, which were previously undetected and to improve the knowledge on the explosive dynamics of the volcano. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8692 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8689 Title: Automatic recognition of landslide seismic signals based on neural network analysis of seismic signals: an application to the monitoring of Stromboli volcano (Southern Italy) Authors: Esposito, A. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Peluso, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: In the last 9 years, the amount and the quality of geophysical and volcanological observations of Stromboli's' activity have undergone a marked increase. This new information highlighted that the landslides on the Sciara del Fuoco flank are tightly linked to the volcanic activity. Actually, at the beginning of the December 28, 2002, effusive eruption, the seismic monitoring network was less dense than now, and therefore it is not known if there was an increase in the landslide rate before the eruption. Despite this, it is known that a big landslide occurred 2 days after the beginning of the eruption which caused a tsunami (December 30, 2002). More recently, the effusive eruption in February 2007 was preceded by an increase in landslides on the Sciara del Fuoco flank, which were recorded by the seismological monitoring system that had been improved after the 2002–2003 crisis. These episodes led us to believe that monitoring the Sciara del Fuoco flank instability is an important topic, and that landslides might be significant short-term precursors of effusive eruptions at the Stromboli volcano. To automatically detect landslide signals, we have developed a specialized neural algorithm. This can distinguish between landslides and the other types of seismic signals usually recorded at the Stromboli volcano (i.e., explosion quakes and volcanic tremor). The discrimination results show an average performance of 98.67 %. According to the experience of the crisis of 2007, to identify changes that can be considered as precursors of effusive eruptions, we set up an automatic decision-making method based on the neural network responses. This method can operate on a continuous data stream. It calculates a landslide percentage index (LPI) that depends on the number of records that are classified by the net as landslides over a given time interval. We tested the method on February 27, 2007, including the beginning of the effusive phase. The index showed an increase as early as at 09:00 UTC on that day and reached its maximum value (100 %) at 12:00, about 40 min before the onset of the eruption. After the beginning of the effusive phase, the index remains high due to the blocks that roll down along the slope from the front of the lava flow. On the basis of these tests, we propose a decision-making method that is able to recognize a trend in the LPI similar to that of 2007 eruption, allowing the identification of precursors of effusive phases at the Stromboli volcano. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8689 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8687 Title: Automatic analysis of seismic data by using Neural Networks: applications to Italian volcanoes Authors: Giudicepietro, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Esposito, A; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; D'Auria, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Martini, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Scarpetta, S.; Università di Salerno Editors: Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Zollo, A.; Università di Napoli Federico II Abstract: The availability of the new computing techniques allows to perform advanced analysis in near real time, improving the seismological monitoring systems, which can extract more significant information from the raw data in a really short time. However, the correct identification of the events remains a critical aspect for the reliability of near real time automatic analysis. We approach this problem by using Neural Networks (NN) for discriminating among the seismic signals recorded in the Neapolitan volcanic area (Vesuvius, Phlegraean Fields). The proposed neural techniques have been also applied to other sets of seismic data recorded in Stromboli volcano. The obtained results are very encouraging, giving 100% of correct classification for some transient signals recorded at Vesuvius and allowing the clustering of the large dataset of VLP events recorded at Stromboli volcano. Mon, 31 Dec 2007 23:00:00 GMT http://hdl.handle.net/2122/8687 2007-12-31T23:00:00Z http://hdl.handle.net/2122/8685 Title: Studio di fattibilità per il monitoraggio delle deformazioni del fondo marino tramite GPS su una meda elastica (Golfo di Pozzuoli – Campi Flegrei) Authors: De Martino, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Guardato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Tammaro, U.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; Iannaccone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia Abstract: The continuous measurement of ground deformations is an important contribution to the monitoring of volcanic areas. When the volcano is totally or partially submerged, the traditional geodetic methods cannot be applied and the measures of seafloor deformation are extremely difficult and expensive. This paper describes the installation of a continuous GPS station on an elastic beacon. The measurements were conducted in the Campi Flegrei Caldera (Gulf of Pozzuoli, Naples), whose vertical displacements are related to the bradyseismic phenomenon. Experimental observations show that it’s possible to monitor vertical displacement of seafloor with a resolution of a few centimeters, also taking into account for measurement errors (due to weather and sea conditions acting on the elastic beacon). This non expensive technique is relevant at Campi Flegrei area, because it extends the ground deformation monitoring at sea, contributing to a better modeling of the deformation field. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8685 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8645 Title: Tremor-based real time monitoring and early warning on Etna Volcano (Italy): technical aspects and methods Authors: D'Agostino, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Di Grazia, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Ferrari, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Langer, H.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Messina, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Reitano, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Spampinato, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Editors: Corsaro, Rosa Anna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: Twenty-five lava fountains occurred on Mt. Etna from January 2011 to April 2012. In summer 2012 volcanic activity resumed in a milder form within the Bocca Nuova crater, before it came to an essential halt in August 2012. All these unrests offer rich material for testing automatic procedures of data processing and alert systems, running 24/7, in the context of volcano surveillance. We focus on the seismic background radiation – volcanic tremor – which plays a key role in the monitoring of Mt. Etna. Since 2006 a multistation alert system has been established in the INGV operative centre of Catania exploiting STA/LTA ratios. Besides, also the spectral characteristics of the signal, which change correspondingly to the type of volcanic activity, can be exploited for warning purposes. Here we apply Self Organizing Maps and Fuzzy Clustering which offer an efficient way to visualize signal characteristics and its development with time. All these techniques allow to identify early stages of eruptive events, and automatically flag a critical status before this becomes evident in conventional monitoring techniques. Changes of tremor characteristics are related to the position of the source of the signal. The location of the sources exploits the distribution of the amplitudes across the seismic network. The locations were extremely useful for warning, throughout both the flank eruption in 2008 as well as the 2011 lava fountains, during which a clear migration of tremor sources towards the eruptive centres could be noticed in advance. The location of the sources completes the picture of an imminent volcanic unrest, and corroborates early warnings flagged by the changes of signal characteristics. Real time data processing requires computational efficiency, robustness of the methods and stability of data acquisition. The amplitude based multi-station approach is not sensitive to the failure of single stations and therefore offers a good stability. The single station approach, exploiting unsupervised classification techniques, limits logistic efforts, as only one or few key stations are necessary. Both strategies have proven to be insensitive to disturbances (undesired transients like earthquakes, noise, short gaps in the continuous data flow). False alarms were not encountered so far. Stable data acquisition and processing come with a properly designed data storage solution. The reliability of data storage and its access is a critical issue. A cluster architecture has been realized for failover protection, including a Storage Area Network system, which allow easy data access following predefined user policies. We present concepts of the software architectures deployed at INGV Osservatorio Etneo in order to implement this tremor-based multi approach system. We envisage the integration of seismic data and those originating from other scientific fields (e. g., volcano imagery, geochemistry, deformation, gravity, magneto-telluric). This will facilitate cross-checking of evidences encountered from the single data streams, in particular allow their immediate verification with respect to ground truth. Tue, 11 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8645 2012-12-11T23:00:00Z http://hdl.handle.net/2122/8627 Title: Aborted eruptions at Mt. Etna (Italy) in spring 2007 unveiled by an integrated study of gas emission and volcanic tremor Authors: Falsaperla, Susanna; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Behncke, Boris; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Neri, Marco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Langer, Horst; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Pecora, Emilio; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Salerno, Giuseppe; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia Abstract: In spring 2007, a sequence of paroxysmal episodes took place at the Southeast Crater of Mt. Etna, Italy. Eruptive activity, characterised by Strombolian explosions, lava fountains, emission of lava flows and tephra, were all associated with an outstanding increase in the amplitude of volcanic tremor. In periods of quiescence between the eruptive episodes, recurring phases of seismic unrest were observed in forms of small temporary enhancements of the volcanic tremor amplitude, even though none of them culminated in eruptive activity. Here, we present the results of an integrated geophysical and geochemical data analysis encompassing records of volcanic tremor, thermal data, plume SO2 flux and radon over two months.We conclude that between February and April 2007, magma triggered repeated episodes of gas pulses and rock fracturing, but failed to reach the surface. Our multidisciplinary study allowed us to unveil these ‘aborted’ eruptions by investigating the long-temporal evolution of gas measurements along with seismic radiation. Short-term changes were additionally highlighted using a method of pattern classification based on Kohonen Maps and Fuzzy Clustering applied to volcanic tremor and radon data. Sat, 31 Mar 2012 22:00:00 GMT http://hdl.handle.net/2122/8627 2012-03-31T22:00:00Z http://hdl.handle.net/2122/8626 Title: Active faults on the eastern flank of Etna volcano (Italy) monitored through soil radon measurements Authors: Neri, Marco; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Giammanco, Salvatore; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Ferrera, Elisabetta; Università degli Studi di Catania, Dip. Scienze della Terra; Patanè, Giuseppe; Università degli Studi di Catania, Dip. Scienze della Terra; Zanon, Vittorio; Centro de Vulcanologia e Avaliação de Riscos Geológicos - Universidade dos Açores Abstract: This study concerns measurements of radon and thoron emissions from soil carried out in 2004 on the unstable eastern flank of Mt. Etna, in a zone characterized by the presence of numerous seismogenic and aseismic faults. The statistical treatment of the geochemical data allowed recognizing anomaly thresholds for both parameters and producing distribution maps that highlighted a significant spatial correlation between soil gas anomalies and tectonic lineaments. In particular, the highest anomalies were found at the intersection between WNW-ESE and NW-SE -running faults. The seismic activity occurring in and around the study area during 2004 was analyzed, producing maps of hypocentral depth and released seismic energy. These maps revealed a progressive deepening of hypocenters from NW to SE, with the exception of a narrow zone in the central part of the area, with a roughly WNW-ESE direction. Also, the highest values of seismic energy were released during events in the southern and northwestern sectors of the area. Both radon and thoron anomalies were located in areas affected by relatively deep (5-10 km depth) seismic activity, while less evident correlation was found between soil gas anomalies and the released seismic energy. This study confirms that mapping the distribution of radon and thoron in soil gas can reveal hidden faults buried by recent soil cover or faults that are not clearly visible at the surface. The correlation between soil gas data and earthquake depth and intensity can give some hints on the source of gas and/or on fault dynamics. Lastly, an important spin-off of this study is the recognition of some areas where radon activity was so high (>50000 Bq/m3) that it may represent a potential hazard to the local population. In fact, radon is the leading cause of lung cancer after cigarette smoke for long exposures and, due to its molecular weight, it accumulates in underground rooms or in low ground, particularly where air circulation is low or absent. In the investigated area this risk is real, as it is inhabited by thousands of people who reside there all year long. Therefore, this study serves as a starting point for the assessment of radon hazard in the Mt. Etna area, considering both spatial and temporal changes in soil radon emissions depending on the presence of faults and/or the occurrence of seismic activity. Sat, 31 Mar 2012 22:00:00 GMT http://hdl.handle.net/2122/8626 2012-03-31T22:00:00Z http://hdl.handle.net/2122/8583 Title: An innovative method for continuous measurement of soil CO2 flux Authors: De Gregorio, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Camarda, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Cappuzzo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Gurrieri, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: Herein, we present a method for continuous measurement of soil CO2 flux that is completely new and distinct from existing instruments. The foremost difference is that instead of using an infrared gas analyser (IRGA), the new device measures soil CO2 flux by means of a simple pressure sensor, measuring pressure transients inside a closed polymeric tube inserted into the soil. This allows continuous measurements even in soil placed in environments that could potentially damage IRGA. In addition, due to the innovative operating principle, measurements of soil CO2 flux can be effortlessly performed also in strongly harsh weather conditions. Theoretical equations were derived for calculating soil CO2 flux solely using measured transient values. The reliability of the equations was rigorously tested with a variety of experiments. Continuous measurements over four months, acquired in a high-emission area on the Island of Vulcano, compared favourably with the data obtained using an established method. Thu, 28 Feb 2013 23:00:00 GMT http://hdl.handle.net/2122/8583 2013-02-28T23:00:00Z http://hdl.handle.net/2122/8580 Title: Continuous monitoring of fumarole temperatures at Mount Etna (Italy) Authors: Madonia, P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Rizzo, A. L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Diliberto, I. S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia; Favara, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Palermo, Palermo, Italia Abstract: In this paper we present the first data of temperature continuously recorded in two fumarole fields (designated VOR and HOR) located in the summit area of Mount Etna volcano (Italy). The time series embraces two distinct periods: (1) October 2007 to November 2009, during which an effusive eruption occurred from May 2008 to July 2009, and (2) November 2011 to June 2012, characterized by the occurrence of strong paroxysms (fire fountains and lava flow). The analysis of the temperature signal in both the time and frequency domains, and its comparison with meteorological observations allowed us to separate the exogenous influences from the effects of variations in the activity state of the volcano. The acquired data were weakly affected by seasonal cycles of the air temperature and strongly affected by the rainfall. Optimization of site conditions (i.e., sensor depth and soil permeability) markedly reduced meteorological disturbances. The distance from the main degassing and/or eruptive fractures was crucial to maximizing the probability of the technical survival of the monitoring apparatus, which was seriously affected by the emission of acidic gases, tephra fallout, and lava flows. Apart from the exogenous influences, the most appreciable variation was observed at VOR, where a huge increase in fumarole temperature was detected immediately after the onset of the 2008–2009 eruption. Such an anomalous increase was attributed to the rapid ascent of magma feeding the eruptive fracture. Another abrupt increase in temperature was recorded at HOR in March and April 2012. During this period the frequency of paroxysm occurrence increased markedly, and this led us to hypothesize that the thermal anomaly was due to the intrusion of a new batch of magma in the conduits of the southeast crater. Medium- to long-term monitoring (weeks to months) of fumarole temperatures revealed variations that were attributed to pressurization/depressurization phases of the shallow volcanic system, which varied between the various monitored sectors of the volcano. Our observations suggest that continuous monitoring of fumarole temperature can give useful information about the activity of Mount Etna. Moreover, due to the complexity of its shallow plumbing system, we conclude that the monitoring systems should be extended to cover the entire fumarole network of the summit area. Thu, 28 Feb 2013 23:00:00 GMT http://hdl.handle.net/2122/8580 2013-02-28T23:00:00Z